1. Field of the Invention
This invention relates to the field of disk drives and to a method of synchronizing a plurality of individual disk drives joined in parallel.
2. Background Art
Data intensive computer applications such as graphics applications, satellite data transmission applications, real time system applications, three dimensional rendering and military applications require the ability to transfer large amounts of data at high transfer rates. In the past, Winchester hard disk drives have been used to provide the storage and data transfer capabilities for computer systems applications. As data transfer requirements have risen, incremental changes and improvements in disk drive performance have been made to keep pace. For example, data and track density increases, media improvements and a greater number of heads and disks have resulted in higher data transfer rates. A disadvantage of such incremental improvements is the large research and development costs associated with each improvement. In addition, as the capacity of any single disk increases, the latency of the disk becomes a factor in performance. Latency is the average time it takes a read/write head to reach a desired data location on a particular track and is a function of the size of the disk rotation speed. The rotation rate of hard disk drives is standardized at 3600 RPM. Therefore, for a single disk, the latency is essentially a fixed value.
To improve bandwidth, it is necessary to divide the data transfer among a plurality of disks. The data is broken up into chunks that may be accessed simultaneously or consecutively from a number of drives. By linking a plurality of drives, a parallel stream of data may be achieved. This increases the band width of the data transfer for improved performance. In addition, the latency can be reduced by dividing a data stream among several drives. In the prior art, drives were linked in parallel and coupled to buffers as an intermediate mechanism to allow synchronization of the data for transfer to a processing means. However, because the data must be buffered prior to output, these prior art systems, are not suitable for "real time" applications.
Therefore, it is an object of the present invention to provide a method of synchronizing a plurality of disk drives.
It is another object of the present invention to provide a low cost method of achieving high data transfer rates utilizing a plurality of low cost Winchester disk drives.
It is yet another object of the present invention to provide a method of synchronizing the indexes of a plurality of disk drives.
It is yet another object of the present invention to provide a method of synchronizing a plurality of disk drives to a common index signal.